1. Field of the Invention
This invention relates to a device for coupling a lever to the piston of a control cylinder.
The invention finds particular application in a hydraulic clutch cylinder in which a rod mounted on a ball element and movable in translation has to be able to displace a piston in alternating motion in one direction and then in another, without axially disconnecting the piston, all being sealed inside a body.
2. Discussion of the Related Art
Already known in this technical field is Swiss patent CH 404 318, which describes a coupling between a straight rod and a piston. For this purpose, the end of the rod is provided with a ball element which is nested in an insert mounted in a hollow portion of the piston. This ball element provides the coupling between the rod and the insert. In opposition to this knuckle joint, lugs of the insert are spaced out by seaming using a suitable tool, these lugs extending through an aperture formed in a transverse wall of the piston (which may for example separate a hollow chamber including a volume of oil from a chamber in which the insert and part of the rod are located). These lugs thus provide the coupling between the insert and the piston. The alternating straight line motion of the rod is therefore transmitted to the piston via the said insert which is fixed to both the piston and the rod.
Now, in this prior art, the coupling is not very satisfactory because excellent sealing has to be ensured at the transverse wall, since oil leaks must not take place. The seaming operation and the use of lugs which, once they have been bent back, are engaged against inclined surfaces of the said wall, does not provide such sealing.
In addition, the seaming operation adds an additional step to the assembly process, and can over time become less and less accurate (thus giving rise to problems of sealing as mentioned above). The seaming operation may damage the transverse wall of the piston, which is fragile.
Finally, it is necessary to avoid any machining or operations involving mechanical deformation (such as bending or seaming) of the piston, in particular if the latter is surface treated (for example anodised aluminium), because the layer which is formed could be damaged. It is therefore of course out of the question to envisage any coupling of the screw type, or the forming of any internal groove in the piston in which to mount a sleeve blocking straight line movement of the rod with respect to the piston.
Accordingly, it is in this context that the invention proposes to resolve at least some of these drawbacks.
To this end, there is proposed a device comprising:
a rigid rod movable in straight line and/or rotary motion and having one end which penetrates into the interior of a hollow portion of a piston, and which is fixed by means of a knuckle joint to the hollow portion of the piston directly or through an interposed insert, the said insert being accordingly mounted inside the hollow portion of the piston, and
means for axial immobilisation of the insert or rod with respect to the piston,
characterised in that the said immobilising means comprise an abutment carried by the piston to ensure axial immobilisation in a direction corresponding to the direction in which the rod is fitted in the piston, and a washer carried by the insert or rod, the said washer having radially elastically deformable peripheral fins which bear against the internal wall of the hollow portion of the piston by deforming in order to ensure immobilisation of the insert or rod in the opposite direction.
Preferably, the abutment will consist of a solid transverse partition wall against which the insert or rod bears once fitted, the said partition wall separating the hollow portion of the piston from a chamber which can contain a hydraulic liquid, the lugs of the washer will define a cone and will extend radially from a central crown portion of opposite conicity, and the washer will be disposed in the hollow portion of the piston in such a way that the conicity of the lugs opposes withdrawal of the rod.
According to further features of the device:
the insert will be able to comprise at least one rigid sleeve fixed on one side to the ball element of the rod and having means for receiving the washer and holding it in position.
the sleeve will be arranged to co-operate, in opposition to the knuckle joint, with an intermediate member for positioning and maintaining the washer with respect to the insert, or with a preform projecting from a solid transverse wall of the piston.
the sleeve will therefore, in particular, be able to have, in opposition to the knuckle joint, a skirt with radially elastically deformable lugs, the said skirt being formed with an external groove for receiving the washer, the skirt being adapted to be connected around the intermediate member or the preform, in such a way as to retain the washer radially and axially in position around the said skirt of the insert, at the level of the said groove. In accordance with a complementary aspect, the skirt will be able to be provided with a reinforcing internal core, and the intermediate member or the preform will be adapted to be inserted between the core and the said skirt.
in an alternative arrangement, the sleeve will also be able to be provided with an aperture in opposition to the knuckle joint, and a projecting portion of the intermediate member or preform will then be able to cooperate with the said aperture in such a way as to maintain the washer radially and axially in position between the sleeve and the intermediate member or preform, at the level of an external shoulder of the said sleeve.
in accordance with another possibility, the sleeve will preferably be provided with an open ended hole opposite the knuckle joint, and the intermediate member will then be provided with a skirt having radially elastically deformable lugs, the said skirt being provided at its end with hook means of a clip type in cooperation with the open ended hole of the sleeve, whereby to retain the washer axially in place between the sleeve and the intermediate member, at the level of an external shoulder of the latter.
in accordance with yet another embodiment, the sleeve will have, in opposition to the knuckle joint, a substantially spherical hollow zone in cooperation with a projecting element which is also substantially spherical and which is part of the intermediate member, whereby to couple the sleeve to the intermediate member by means of a knuckle joint, the washer being then interposed and blocked between the sleeve and the said intermediate member, at the level of a shoulder of the intermediate member.
The invention also relates to a hydraulic clutch cylinder for a motor vehicle comprising a device of the kind described above.